The present invention relates to a shredded tobacco feeding apparatus within a cigarette manufacturing machine and, more particularly, to a shredded tobacco feeding apparatus for forming cigarettes which have uniform quality and high expanded-bulkiness.
It is important for a cigarette manufacturer to maintain a good quality of cigarette and to stabilize the quantity of shredded tobacco for filling in the cigarette. To eliminate the irregularity of the filling quantity of shredded tobacco renders a significant cost reducing effect of the shredded tobacco. In recent years, the price of leaf tobacco has gone up, increasing the importance of cost reduction even further. Therefore, cigarette manufacturers have made various attempts to save tobacco by, for example, reducing the irregularity of the weight of the manufactured cigarettes, increasing the expanded bulkiness by reducing the undue crushing of shredded tobacco, or otherwise by expanding the shredded tobacco by means of a special treatment in order to improve its property of expanded bulkiness.
Because of the foregoing, suppliers of cigarette manufacturing machines are also expected to supply a machine in that the irregularity of the weight of cigarette is small and the expanded bulkiness of shredded tobacco is high.
This means that the evaluation of a shredded tobacco feeding apparatus in a cigarette manufacturing machine is made based on the above mentioned two characteristics, i.e., weight and expanded bulkiness. To this end, heretofore, many proposals have been made. To reduce the irregularity of the weight of cigarette, there is proposed a density detecting method using radioisotopes with the help of marvelous development of electronic art particularly in recent years. Especially, the improvement of the controlling device has been progressed as such that a density detecting apparatus is used therein as a detecting element. One such example can be seen in Japanese Patent Application Early Publication No. 51(1976)-95198 wherein the irregularity of the weight of cigarette is markedly reduced. The concern of a cigarette manufacturer is now directed to a machine enabling to produce expanded bulky shredded cigarette and more particularly to a feeding apparatus of shredded tobacco.
On the other hand there are two factors which affect adversely efforts directed toward the improvement of the expanded bulkiness of cigarette in a cigarette manufacturing machine. One of them is; if the length of a grain of shredded tobacco is made long or in other words, if the length of the fiber shape of shredded tobacco is made as long as possible for filling, the expanded bulkiness of cigarette is improved. However, it is known that the irregularity of the weight of cigarette is increased. From the foregoing, the maker of cigarette knows that the length of the tobacco grain should preferably be in the range from about 1.5 to 4 mm. It should be noted that the term "the length of the grain" when used herein refers to substantially the desired size of a mesh of a screen for shredded tobacco.
The other factor resides in the fact that the length of the grain of shredded tobacco which is fed to a cigarette manufacturing machine becomes shorter in recent years. This is chiefly attributable to the transition of the quality of raw leaf tobacco material and to the change of treatment on the raw leaf tobacco. Consequently, it becomes impossible to maintain a sufficient expanded-bulkiness by means of the conventional picking method.
In view of these problems, many improvements have been made on a shredded tobacco feeding apparatus in a cigarette manufacturing machine. For example, a method is proposed to selectively pick up only long shredded tobacco by pin as disclosed in Japanese Patent Application Early Publication No. 52(1977)-151798. However, according to this method, short shredded tobacco is also picked up together with long shredded tobacco since the former is involved in the latter in an entangled fashion. Undue crushing of shredded tobacco is not desirable.